A wide variety of gas purge valves are known in the art, deigned for fitting on different fluid systems and configured for different purposes e.g. pressure control, discharge of residual gas within a liquid in the system, etc.
For example, U.S. Pat. No. 4,770,201 discloses a fluid flow valve such as a faucet or air-purge valve comprising a housing having defined therein a fluid through-flow aperture with a valve seating formed in the housing and bounding said aperture. A flexible closure membrane is secured at one end to the housing and is adapted to be biased, under fluid pressure in the housing, against the valve seating so as to seal the aperture. Membrane displacing means are secured to an opposite end of the membrane so that displacement of the displacing means in a first sense progressively detaches successive transverse portions of the membrane from the seating so as to open the aperture while displacement of the displacing means in an opposite sense allows for the membrane to become sealingly biased against the seating.
A gas purge valve is disclosed in U.S. Pat. No. 7,617,838 directed to a gas purge valve comprising a housing formed with an inlet and an outlet formed with a valve seating, and a sealing assembly comprising a sealing member displaceable between an open position and a closed position. The sealing assembly is supported by an external support lever mechanism extending outside the housing, to thereby displace the sealing assembly into sealing engagement with the valve seating at the closed position.
U.S. Pat. No. 6,105,608 is directed to a gas purge valve comprising a valve housing that has a valve inlet and major and minor valve outlets, a valve partition mounted in the housing divides the housing into a first chamber communicating with the valve inlet and a second chamber that communicates with the minor valve outlet. A restrictive flow passage is defined in the housing that effects communication between the first and second chambers and has a through flow rate less than that of the minor valve outlet. A minor valve closure device is provided for closing the minor valve outlet to liquid to outflow. A differential pressure responsive device mounted in the partition member and displaceable in response to a pressure differential between the chambers and a major valve outlet obturating device responsive to displacement of the differential pressure responsive device into the opening of the major valve outlet when the pressure differential exceeds a predetermined magnitude.